It is known in the art relating to diesel engines that future governmental emissions regulations require improvements in engine design in order to reduce emissions to meet or exceed these regulations. For example, enhanced air system designs could provide higher rates of cooled EGR (exhaust gas recirculation), thereby reducing NOx emissions, while enhanced fuel injection systems could reduce the inevitably higher soot emissions that would result from the use of higher EGR rates. Also, combined soot and NOx emissions aftertreatment systems could reduce emissions from diesel engines. Exhaust aftertreatment systems, however, can be costly and therefore are not the most desirable means of achieving emissions reductions.
In contrast, advancements in the combustion system design could reduce emissions while minimizing the need for costly and unproven diesel exhaust aftertreatment systems. Further, fuel economy, exhaust emissions, and performance of diesel combustion systems are greatly affected by the design of the engine's piston, as well as by the choice of fuel injection and air handling equipment (e.g., turborcharger, EGR system, etc.). Therefore, improvements in diesel engine piston design could advantageously lead to lower emissions without significant increases in cost.